探针作用力和溶剂效应下分子器件结构和输运性质研究

As silicon-based electronic devices approach the limit of traditional devices, the design and preparation of new electronic devices based on organic molecules possess important scientific significance and practical value. It has been demonstrated that the performance of molecular devices is closely related to the structure of the molecular devices both experimentally and theoretically, however great challenges are faced for the experiments to determine the structure of molecular devices by themselves. The combination of experimental results of inelastic electron tunneling spectroscopy with theoretical simulations based on the density functional theory (DFT) provides an effective way for the detection of molecular devices structures. Nevertheless, the tip pressure and the solvent can induce significant change of the device structures. This project will focus on the study of the tip pressure and the solvent effect on the transport properties in the systems composed of STM tip/molecule(s)/electrode. The strategies are as follows. First, the preparations of molecular devices are simulated by performing the molecular dynamic simulations where the solvent are also included. Consequently, the inelastic electron tunneling spectra of thousands of molecular devices with different configurations will be studied with the inelastic scattering Green's function theory based on the first-principles calculation of the electronic structures and frequencies of the generalized molecular devices. The influence of the tip pressure and the solvent on the device structures as well as the spectra will be analyzed statistically. This project will build the direct and intuitive relationship between the tip pressure and the solvent effect on the device structures and the spectra, which will do great favor for us to understanding the experimental results and determining the device structures.

由于硅基电子器件的尺寸趋于传统器件的极限，研制和开发基于有机分子的新电子器件就具有重要的意义。实验和理论研究表明分子器件的性能同其结构关系密切，但仅凭实验确定其结构存在很大的挑战，非弹性电子隧穿谱的实验技术与基于密度泛函理论（DFT）的模拟相结合为探测器件的结构信息提供了有效的手段。分子器件制备过程中针尖压力以及溶剂分子对分子器件的结构具有很大的影响。本项目将针对探针/分子/电极的体系重点研究分子结制备、测量过程中针尖压力和溶剂效应对分子器件结构和输运性质的影响。包括：利用分子动力学的方法模拟分子器件制备过程，包含溶剂的影响；然后，利用基于DFT的非弹性散射格林函数的方法计算大量分子器件的非弹性电子隧穿谱，并对其结构和光谱的关系进行统计研究，揭示针尖压力、溶剂对结构及光谱的影响。项目的研究将为压力和溶剂对器件结构以及光谱的影响建立直观的关系，为人们理解光谱和确定器件结构提供重要的依据。

由于硅基电子器件的尺寸趋于传统器件的极限，研制和开发基于有机分子的新电子器件就具有重要的意义。实验和理论研究表明分子器件的性能同其结构关系密切，但是对分子器件实际构型的表征存在很大困难，基于密度泛函理论（DFT）的第一性原理模拟可以为探测器件的结构信息提供有效的手段。本项目采用第一性原理计算的方法得到了有机分子形态、输运性质与外力的关系；研究了溶剂效应（H键）对有α羟苯基吡啶基团的分子二极管的电输运特性影响，设计了多分子内氢键的结构体系；研究了烷烃硫醇分子碳链长度和奇偶对有机分子器件非弹性电子隧穿谱的影响，证实了C-H伸缩振动的来源；并进一步研究了分子间作用力对辛烷硫醇分子结非弹性电子隧穿谱的影响，发现链间隧穿与分子间耦合系数密切相关，得到了分子间距、耦合系数和隧穿通道之间的关系以及非弹性电子隧穿谱和分子器件结构之间的关系。